The conventional method for effecting surgical attachments involves the time-honored technique of sewing with needle and suture. Over the years a wide variety of needle sizes and shapes and suture sizes and compositions have been developed to meet the demands of many different suturing situations. More recently, other methods and means have been developed as an alternative to conventional suturing. For example, a great deal of work has been done in the area of surgical stapling.
In U.S. Pat. Nos. 4,006,747 and 4,235,238, surgical fasteners are disclosed which can be used to attach two or more tissue members to one another, e.g. so as to close a surgical incision. These surgical fasteners generally comprise a relatively short, flexible filament having a relatively rigid, bar-like head on each end thereof, wherein the bar-like head normally resides perpendicular to the adjoining length of filament during use. These surgical fasteners, sometimes referred to as "T-bar" fasteners due to their shape, are deployed using a special tool which, in cooperation with the tissue members being joined, causes one of the fastener's heads and the adjoining length of filament to be temporarily aligned with one another, whereby that head and the filament can be threaded through the two or more tissue members which are being joined. The several tissue members are then captivated on the filament between the fastener's two bar-like heads.
In certain circumstances it may be desirable to have the surgical fasteners disposed so that at least one end thereof is anchored inside body tissue, rather than simply bearing inwardly against the outer surface of the body tissue as with the T-bar fasteners described above. See, for example, U.S. Pat. No. 3,716,058, which discloses a short section of suture material having a return barb on each end. Some attention has been directed towards utilizing T-bar fasteners in a similar manner. For example, T-bar fasteners have been used for attaching informational tags to meat, wherein one end of the T-bar fastener is anchored inside the meat while the other end is allowed to dangle free outside the meat, with the tag attached. In this respect it should be noted, however, that all of the T-bar fasteners known to date comprise arrangements wherein the end surfaces of the fastener's bar-like heads are formed either flat (see, for example, U.S. Pat. Nos. 2,069,878, 3,990,619, 4,006,747, 4,039,078 and 4,235,238) or effectively rounded (see, for example, U.S. Pat. Nos. 3,103,666, 3,399,432, 3,470,834, 3,494,004, 3,931,667 and 3,979,799). As a result, the holding power of the T-bar fasteners is quite limited. In the meat tagging application described above, the limited holding power provided by the flat or effectively rounded end surfaces of the fastener heads is not only tolerable but actually desirable, since it allows the fasteners to be easily pulled out of the meat upon the application of a moderate pulling force, e.g., when the meat is being prepared for cooking.
However, such a construction is clearly not acceptable in the case of surgical applications where it may be critical that the T-bar fasteners remain solidly anchored in the body tissue despite the application of a substantial pulling force.